This invention relates to hydrophilic polymer coatings having antimicrobial properties.
A number of metal ions have been shown to possess antibiotic activity, including silver, copper, zinc, mercury, tin, lead, bismutin, cadmium, chromium and thallium ions. It is theorized that these antibiotic metal ions exert their effects by disrupting respiration and electron transport systems upon absorption into bacterial or fungal cells. Antimicrobial metal ions of silver, copper, zinc, and gold, in particular, are considered safe for in vivo use. Antimicrobial silver ions are particularly useful for in vivo uses due to the fact that they are not substantially absorbed into the body.
Silver ions have been impregnated in the surfaces of medical implants, as described in U.S. Pat. No. 5,474,797. Silver ions have also been incorporated in catheters, as described in U.S. Pat. No. 5,520,664. The products described in these patents, however, do not exhibit an antibiotic effect for a prolonged period of time because a passivation layer typically forms on the silver ion coating. This layer reduces the release rate of the silver ions from the product, resulting in lower antibiotic effectiveness. In addition, the layer containing the silver frequently becomes discolored, causing the products to have a poor appearance. The discoloration is caused by a high flux release rate of silver ion into the surroundings.
Antibiotic zeolites can be prepared by replacing all or part of the ion-exchangeable ions in zeolite with antibiotic metal ions, as described in U.S. Pat. Nos. 4,011,898; 4,938,955; 4,906,464; and 4,775,585. Polymers incorporating antibiotic zeolites have been used to make refrigerators, dish washers, rice cookers, plastic film, chopping boards, vacuum bottles, plastic pails, and garbage containers. Other materials in which antibiotic zeolites have been incorporated include flooring, wall paper, cloth, paint, napkins, plastic automobile parts, bicycles, pens, toys, sand, and concrete. Examples of such uses are described in U.S. Pat. Nos. 5,714,445; 5,697,203; 5,562,872; 5,180,585; 5,714,430; and 5,102,401.
Hydrophilic coatings with low friction have been applied to medical devices such as catheters. See, for example, U.S. Pat. No. 5,509,899. Such coatings are highly desirable to allow for easy insertion into the body. Hydrophilic coatings, however, are excellent breeding grounds for bacteria.
U.S. Pat. No. 4,923,450 discloses a catheter having a coating of antibiotic zeolite. U.S. Pat. No. 5,100,671 describes a medical article that is formed using silicone rubber that contains antibiotic zeolite. However, use of conventional antibiotic zeolite, such as that described in U.S. Pat. No. 4,011,898, results in a catheter which exhibits severe discoloration. For example, a catheter made according to U.S. Pat. No. 4,923,450 which has a coating of the antibiotic zeolite material of U.S. Pat. No. 4,011,898 adhered to its surface becomes highly discolored within days.
A conventional catheter is typically comprised of a hydrophobic polymer. When antibiotic zeolite is incorporated in such a catheter, however, water is unable to reach the zeolite in the bulk of the material. The bulk of the zeolite is, therefore, ineffective against bacteria surrounding the catheter since only the zeolite at the surface of the catheter is active.
U.S. Pat. No. 5,305,827 describes an antimicrobial hydrophilic coating for heat exchangers. The coating includes silver oxide, to inhibit microbial growth and improve adhesion to the heat transfer surfaces of a heat exchanger. However, this coating exhibits severe discoloration and is typically antimicrobially effective for 3 days or less.
Japanese Pat. Application No. 03347710 relates to a non-woven fabric bandage containing synthetic fibers and hydrophilic fibers. The synthetic fibers contain zeolite which is ion-exchanged with silver, copper, or zinc ions.
U.S. Pat. No. 4,923,450 discloses incorporating zeolite in bulk materials. When zeolite is conventionally compounded into polymers, however, the zeolite often aggregates, causing poor dispersion of the zeolite in the polymer. When such material is molded or extruded, the surface of the polymer is frequently beaded instead of flat. Poor dispersion of the zeolite also can cause changes in the bulk properties of the polymer, such as a reduction in tensile strength. Any significant changes in the bulk properties of medical devices, such as catheters, however, result in a need to seek regulatory clearance by the U.S. Food and Drug Administration (FDA), which is a costly and time consuming process.
Furthermore, it has been found by the present inventors that conventionally kneading antibiotic zeolites in many polymeric materials results in a xe2x80x9chazyxe2x80x9d appearance and in discoloration. This appears also to result from inadequate dispersion of the zeolite, i.e., the formation of zeolite aggregates in the material, and the inclusion of air or water during the kneading process.
U.S. Pat. No. 4,938,958 describes antibiotic zeolites in which a portion of the ion-exchangeable ions in the zeolite are replaced with amnmonium. This results in a product which exhibits reduced discoloration. However, as described in U.S. Pat. No. 4,938,955, it is often necessary to add an organic discoloration inhibitor, in addition to the antibiotic zeolite, to adequately prevent discoloration of the resin in which the zeolite is incorporated. Discoloration inhibitors are often not biocompatible and cannot be incorporated into medical devices. Furthermore, incorporation of an organic discoloration inhibitor in the polymeric material of a medical device may cause changes in the bulk properties of the material that are highly undesirable.
Therefore, there is a need for a hydrophilic polymer coating which contains an antimicrobial material which releases antibiotic metal ions and avoids antibiotic particle aggregation. Furthermore, there is a need for a hydrophilic polymer coating which contains an antimicrobial material which does not discolor.
The invention relates to a substrate having an antibiotic coating composition coated thereon. The coating composition is formed of a hydrophilic polymer having antibiotic ceramic particles dispersed therein, preferably, without substantial aggregation of the particles.
Also, an article is provided comprising a substrate on which is coated an antibiotic hydrophilic coating composition. The coating composition comprises a hydrophilic polymer having antibiotic ceramic particles dispersed therein.
In another embodiment, the invention relates to a coating solution comprising a hydrophilic polymer having antibiotic zeolite particles dispersed therein and an organic solvent.
Yet another embodiment of the invention is a method for preparing an antibiotic hydrophilic coating on a substrate. The method involves applying an antibiotic hydrophilic coating solution comprising a hydrophilic polymer, dispersed antibiotic ceramic particles, and an organic solvent, to the substrate.